[ Electrical sewage and wastewater treatment apparatus and instruments, namely, stirrers, hyperboloid stirrers, drawing devices for stirrers, submersed motors or stirrers, fillings for trickling filters, sewage and sludge pumps, mixers, agitators, all for the use in the automatic operation of sewage clarification plants and wastewater treatment plants; electrical sewage and wastewater treatment apparatus and instruments, namely stirrers, hyperboloid stirrers, drawing devices for stirrers, sub...